Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 281845
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
145 PM CDT Wed Jun 28 2017

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 321 AM CDT Wed Jun 28 2017

Fairly widespread convection over E NE/Dakotas in MN and W IA
early this AM ahead of what appears to be a couple of
convectively enhanced shortwaves and within strong warm/moist
advection aided by 40-45+ kt SSW LLJ. This activity is expected
to migrate eastward into cwa and also develop withing warm
advection wing. Latest SPC Mesonalysis shows modifying airmass
along/ahead of convection with MUCAPE surging to 1000-2000 j/kg
with effective bulk shear 45-50 kts certainly supportive of some
strong storms to possibly isolated severe this morning west of
the Mississippi River.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 321 AM CDT Wed Jun 28 2017

Convectively enhanced shortwaves and LLJ with strong warm/moist
transport will lead to high confidence of showers and storms
for a good portion of the area today. AM activity will maintain
a few stronger to possibly isolated severe cores given
strong effective bulk shear and increasing instability. The
main threat would be hail, with possibly some gusty winds as
well. Do anticipate a decreasing trend in activity by late AM
through midday, but likely festering at least some activity
all day given lift from shortwaves. Several CAMs then support
more robust redevelopment to occur back from central into
northeast IA ahead of surface boundary. The challenge is how
much recovery or destabilization can occur in wake of this
mornings activity, which leads to a somewhat conditional risk
for severe weather this afternoon/evening. Several CAMs suggest
redevelopment to occur back from central IA into northeast IA by
mid afternoon tracking eastward into this evening. If sufficient
recovery/destabilization occurs ahead of this afternoon
development then severe weather is likely given presence of
strong deep layer shear, with 0-6km bulk shear 40-50 kts. Main
threats would large hail, possibly significant 2+ inch diameter
given strong shear, steep mid level lapse rates and decent omegas
in -20c to -30c layer. Damaging winds to 70 mph would also be a
concern, with even a low risk of tornadoes in presence of
boundaries with strengthening LLJ enhancing curvature in 0-3km.
Vectors favor some potential for discrete cells initially this
afternoon before likely transitioning to one or more linear bands
into this evening. Given the severe potential and magnitude
SPC has placed the cwa in an enhanced risk of severe weather for
mainly this afternoon/evening. Do anticipate the risk of storms
to shift across the south/east cwa this evening and perhaps out
of the cwa by around midnight.

.LONG TERM...(Thursday through Tuesday)
ISSUED AT 321 AM CDT Wed Jun 28 2017

A brief respite from the active weather is anticipated overnight
into Thursday AM. However, by Thursday afternoon and night
strong synoptic scale lift in concert with anomalously high
PWATs of near 2 inches will set the stage for another round of
storms, with areas near/south of I-80 seemingly most favored.
Strong to possibly severe storms and also risk of very heavy rain
is expected with this activity, with veered SWly LLJ favorable
for backbuilding, which could lead to flash flooding concerns in
localized areas.

Another wave of showers and storms is anticipated for late
Friday into Saturday ahead of another wave traversing through
broad Upper Midwest/Great Lakes trough.

Semi-zonal to W/NW flow looks to keep things somewhat unsettled
late weekend through early next week with periodic shower
chances. Temps look to be near normal throughout the period.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
ISSUED AT 145 PM CDT Wed Jun 28 2017

Strong to severe storms are expected across the area this
afternoon through this evening, and possibly much of the night
south of I-80. Some lingering low clouds may produce MVFR
ceilings at CID and DBQ early this afternoon. Otherwise, VFR
conditions will prevail through the afternoon. There is the
potential for low clouds possibly into MVFR range to develop
associated with thunderstorm complexes overnight into Thursday
morning, but confidence was not high enough to include in the
forecasts.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

SYNOPSIS...McClure
SHORT TERM...McClure
LONG TERM...McClure
AVIATION...Sheets



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